Objectives: We evaluated the reliability of sonographic criteria in selecting solid renal masses for percutaneous fine-needle biopsy.
Methods: In study 1 (intraoperative ultrasound study), we prospectively examined 100 consecutive patients scheduled for partial/radical nephrectomy by using two different high-resolution probes (Philips HDI 5000, CT8-4, L12-5; 4-12MHz). The main tumor was intraoperatively evaluated by B-mode and power Doppler sonography. Morphologic characteristics seen on ultrasound were categorized in (non-)homogenous and (non-)cystic renal masses and were related to findings of pathological examination. Study 1 provided the selection criteria for study 2. In study 2 (percutaneous biopsy study), under local anesthesia and with the use of an 18-G needle, we prospectively performed two to three sonographically guided percutaneous biopsies in 30 consecutive patients whose tumors appeared to be homogenous and noncystic according to the sonograph (convex array 3.5MHz, HDI 5000, C5-2 and Falcon 2101 EXL, B+K Medical).
Results: In the ultrasound study, only 16 (22.9%) of the 76 clear-cell carcinomas but all 9 (100%) oncocytoma appeared homogenous and noncystic on high-resolution intraoperative ultrasound. By applying these results to 30 patients of study 2 (18 men, 12 women; aged 63+/-7.7 yr, tumor size 29+/-11.3mm) who met these sonographic criteria on preoperative transabdominal ultrasound, we bioptically diagnosed 8 (26.7%) benign tumors; 25 of 30 (83.3%) patients were accurately diagnosed. Small tumors (<3cm), decreased breathing compliance, and medially located renal lesions seem to negatively influence biopsy results.
Conclusions: Kidney tumors that appear noncystic and homogenous on preoperative ultrasound are more likely to be of benign origin. Ultrasound-guided percutaneous biopsy of these solid renal masses could determine renal tumor patients for whom surveillance might be an option. However, experienced and dedicated histopathologic evaluation remains crucial to observe patients with clearly benign biopsy results. All even slightly questionable biopsy findings require surgical exploration.